Voltage indicating instrument and case therefor



F. B. BOYLE Feb. 19, 1952 VOLTAGE ITIDICATING INSTRUMENT AND CASE THEREFOR Filed Sept. 28, 1949 INVENTOR 7/2 A r TOR N5 Y Patented Feb. 19, 1952 VOLTAGEINDICATING INSTRUMENT AND CASE: THEREFOR Francis B'. Boyle, Kalamazoo,.Mich-., assignor to- The Wigginton Company, Kalamazoo, Mich., a. corporation ofMichig'an.

Application September 28, 1949, Serial'N'o; 1185209 8r Claims; (CL. 171-95) This invention relates to improvements in volt age indicating instrument and case therefor.

The principal objects of this invention are?- First, to provide a novel form of voltage in-- dicating instrument which contains and protects its test prods when not in use.

Second, to provide a voltage indicating instrument with test leads and prod'swhich can be handled in a plurality of relationships with re spect to the body of the instrument for conveniently reading the dial of the instrument. while applying the prods to electrical circuits being tested.

Third, to provide a novel. form of case for. in expensively retaining the operating elements and: prods of a voltage indicating. instrument;

Fourth, to provide a voltage indicating instrument having means therein for indicating which. of two wires of a circuit is the. live wire.

Other objects and advantages relating to details of my instrument willbe apparent from aconsideration of the following description and; claims. The drawings; or which. there is onesheet, illustrate a preferred. form of my instru-: ment.

Fig. 1 is an elevational view of the instrument and its prods in inactive carrying position.

Fig. 2 is a view of the instrumentwith one. half of the case removed.

Fig. 3 is a transverse cross sectional view takenalong the plane of theline 3-3 in Fig. 2.

Figs. 4, 5 and 6 are views showing, three-positions in which the prods of the instrument maybe positioned relative to the case.

My instrument consists of a case I. formed of similar halves 2 and 2A which are shaped tomeet along a central parting plane 3. Preferably the halves of the case will be molded from plastic; material. The upper end of the case. is generally rectangular while the corners of the lower endof the case are notched inwardly as at. 4 leaving a central projection 5 from which the test leads 6ii extend to a familiar type of test. procl I having an insulating grip or handle. 8.

The back half 2A of. the case. is shaped onits inner side with parallel half round recesses. 9 .ex-. tending along the sides of the case and a central. recess H] adapted to receive the lower half of a. coil H and the movable armature [2. Attention. is called to the fact that the recess I is enlarged intermediate of its ends providing shoulders I3 for engaging the ends of the coil and preventing. longitudinal movement. of the coil in the case; The upper end of therecess ID. is further notched" along the bottom as at M (seeFig: 3') torecei've' a lug l carried on the indicator pin l6 of't'h'e' half. round. recesses Il mating with the recesses 9 in the. back half. The recesses. 9 and I1. form bores extending along the sides of the case and opening through the notched ends of the case to receive theinsulating handles 8- of. the test prods. The front half of the case is also provided with a central recess I8 mating with the recess l-D in the: back half to receive thecoil and is slotted as at l9 to provide an opening for the indicator pin It. The indicia plate 20 is secured to the front half and around the slot l9 andcarries voltage indicia cooperative with the pin [6.

The lower or inner ends of. the central recesses Iii and I8 below the coil ll provide. spaee for the mounting and retension of a resistor 2 and neon lamp 22. The central recess opens through the bottom of the projection 5 forming a passage for I the test leads 6 which are anchored to the case by pins 23. A pair of screws 24 extending through the upper and lower ends of the case hold the two halves of the case together.

Within the case one of the test leads 6 is connected by a wire 25 to one terminal" of the neon lamp and to one end of the'resi'stor 21. The other test lead is connected by a wire 26 to one endof the coil [I1 and. the other end of' the coil is connected by the. wire 27 to the resistor 2|. The free electrode of the neon tube is connected by a wire 28 to a small metal plate 2.9 lying. alongside of the coil II but electrically insulated therefrom;

The. theory of operation of the voltage indicating elements is well known and it will be understood that voltage applied to the" test prod's' will be connected through the resistor and coil to" attract the armature l2 inwardly of the coil against'the resistance of the spring The indicating pin It is thus caused to move along. the slot' [9 to the appropriate voltage indicia on the plate 20. The function of the neon lamp and plate 29 is also well understood in that if the test prod I connected to the neon lamp is applied to a live wire while the instrument is held in inverted or faced downward position sufficient capacitance will be" present between the hand of the operator and the plate 29" to cause the neon lamp to. glow thus indicating that the wire" is energized; A hole 3d in the back half of the case permits the lamp 22 to be viewed when theinstrument is used as a hot wire indicator.

prods-are' retained inthe bores along the sides of the instrument. Annular grooves 3| are formed in the case and around the bores near the upper or outer ends thereof and springable split rings 32 are positioned in these grooves to frictionally grip the sides of the handles 8. Note that the left prod and handle as shown in Fig. 2 abuts its associated split ring and prevents the pointed prod I from accidentally projecting from the case. A slight but definite pressure applied to the lower end of the grip 8 will expand the split ring and permit the grip to move past the ring and project the prod from the outer end of the case as shown by the right prod in Fig. 2. If one prod is drawn completely through its bore until the split ring snaps closed behind the inner end of the grip as shown in Fig. 6 the instrument can then be held 7 in one hand with one prod projecting therefrom for application to a wire or contact to be tested.

tending the full length of the case longitudinally alongside of said first recesses, the corners of the lower end of said case being cut away leaving a projection between the lower ends of said second recesses, a coil received in said first recesses, an armature telescopically slidable in said coil parallel to said second recesses and having an indicating finger visible through one of said parts, test leads entering said case and electrically connected to the ends of said coil, test prods secured to the outer ends of said leads and having insulating handles, said handles being axially slidably receivable in said second recesses, and springable gripping elements projecting into said second recesses near the outer ends thereof and adapted to yieldably engage the ends of said handles to resist the passage of said handles through said second recesses, said prods and handles being of This leaves the operators other hand free to operate and move the other prod to various contacts as desired with the first prod and instrument held in a convenient readable position.

If both prods are pushed completely through the bores in the case the test leads may be looped upwardly through the bores as indicated in Fig. permitting the operator to move the prods about to various contacts while the case of the instrument hangs in an upright position immediately in front of the operator for convenient reading of the instrument scale. Fig. 4 shows the instrument arranged for conventional handling with the test leads and prods extending freely from the base of the instrument.

Having thus described my invention, what I claim as new and desire to secure by Letters Pat- 1 ent is:

1. An electrical testing instrument comprising, a generally rectangular case of greater width than thickness and greater length than width, said case being formed of two parts joined along a longitudinal parting plane extending the width of the case, the meeting faces of said parts having first mating recesses formed therein and a pair of second mating recesses extending the full length of the case longitudinally alongside of said first recesses, the corners of the lower end of said case being cut away leaving a projection between the lower ends of said second recesses, a coil received in said first recesses, an armature telescopically slidable in said coil parallel to said second recesses and having an indicating finger visible through one of said parts, test leads entering said case through said projection and electrically connected to the ends of said coil, test prods secured to the outer ends of said leads and having insulating handles, said handles being axially slidably receivable and laterally retainable in said second recesses, and stops projecting into said second recesses near the outer ends thereof and adapted to engage the ends of said handles to resist the passage of said handles through said second recesses, said prods and handles being of such, a length that the inner ends of said handles project from said case alongside of said projection when the ends of the prods are located within" and adjacent the outer ends of said second recesses and the outer ends of the handles are abutted against said stops.

2. An electrical testing instrument comprising, a generally rectangular case of greater width than thickness and greater length than width, said case being formed of two parts joined along a longitudinal parting plane, the meeting faces of said parts having first mating recesses formed therein and a pair of second matin recesses ex sucha length that the inner ends of said handles project from said case alongside of said projection when the ends of the prods are located within and adjacent the outer ends of said second recesses and the outer ends of the handles are abutted against said gripping elements.

3. A voltage indicating instrument comprising, a case having a central longitudinal recess formed therein, voltage indicating mechanism including a coil and reciprocable armature retained in said recess, test leads electrically connected to said mechanism and extending from said case, said case having a pair of longitudinally extending bores formed therethrough along each side of said recess and parallel to said armature, test prods having insulating grips secured to the outer ends of said test leads and being axially slidably receivable in said bores, said grips being laterally retained when in said bores by the walls thereof, and annular yieldable gripping elements positioned in said bores to engage the ends of said grips and yieldably resist movement of said grips through said bores, two corners of said case being cut away along said bores and said grips being of such a length that the inner ends of said grips project into the cut away areas when the outer ends of said prods are positioned in said bores. I

4. A voltage indicating instrument comprising, a case having a recess formed therein, voltage indicating mechanism including a coil and reciprocable armature retained in said recess, test leads electrically connected to said mechanism and extending from said case, said case having a pair of longitudinally extending bores formed therethrough alongside of said recess and par-- allel to said armature, test prods havin insulating grips secured to the outer ends of said test leads and being axially slidably receivable in said bores, said grips being laterally retained when in said bores by the walls thereof, and annular yieldable gripping elements positioned in said bores to engage the ends of said grips and yieldably resist movement of said grips through said bores in either direction.

5. An electrical testing instrument comprising, a case,test leads extending from said case, saidcase having a pair of longitudinally extending recesses formed therein and extending from end to end thereof, test prods having insulatin grips secured to the outer ends of said test leads and bein axially slidably receivable in said recesses, said grips being fully laterally retained when in said recesses by the walls thereof, and stops in said recesses selectively engageable with the ends of said grips to resist movement of said grips through said re-' cesses.

6. A case for an electrical testing instrument including mechanism for registering an electrical condition and test leads and prods for connecting said mechanism to a circuit comprising, a pair of generally rectangular parts joined together along a longitudinal parting plane, the meeting faces of said parts forming mating central recesses extending longitudinally of the case to receive said mechanism and mating recesses forming passages extending longitudinally of the case on each side thereof and opening through both ends of said case, the corners of one end of said case being notched whereby test prods on the ends of said leads may be axially slidably received and laterally retained in said passages with their inner ends projecting from the notched portions of the case while the outer ends of the prods are positioned within said passages, and stops positioned in said passages adjacent to the outer ends thereof and adapted to engage said test prods to resist movement of said prods in said passages.

7. A case for an electrical testing instrument including mechanism for registering an electrical condition and test leads and prods for connecting said mechanism to a circuit comprising, a generally rectangular body having a central recess extending longitudinally therein to retain said mechanism and longitudinally extending recesses formed therein on each side of said case and opening through both ends of said case, the corners of one end of said case being notched whereby test prods on the ends of said leads may be axially slidably received and laterally retained in said side recesses with their inner ends projecting from the notched portions of the case while the 35 outer ends of the prods are positioned within said side recesses, and stops positioned in said side recesses and adapted to engage said test prods to resist axial movement of said prods in said side recesses, said stops being positioned closer to the outer ends of said side recesses than the inner ends thereof whereby the inner ends of said prods may be selectively positioned in the outer ends of said side recesses and against said stops with the outer ends of said prods projecting outwardly of REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,036,077 Podell Mar. 31, 1936 2,366,991 Wich Jan. 9, 1945 2,458,628 Okun Jan. 11, 1949 2,501,725 Knopp Mar. 28, 1950 FOREIGN PATENTS Number Country Date 128,471 Great Britain June 26, 1919 

